US4511223A - Telecentric variable power illumination system - Google Patents

Telecentric variable power illumination system Download PDF

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Publication number
US4511223A
US4511223A US06/388,200 US38820082A US4511223A US 4511223 A US4511223 A US 4511223A US 38820082 A US38820082 A US 38820082A US 4511223 A US4511223 A US 4511223A
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unit
light source
converging
sub
lens unit
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US06/388,200
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English (en)
Inventor
Hideo Hirose
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Nikon Corp
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Nippon Kogaku KK
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Assigned to NIPPON KOGAKU K.K.; 2-3, MARUNOUCHI 3-CHOME, CHIYODA-KU. TOKYO reassignment NIPPON KOGAKU K.K.; 2-3, MARUNOUCHI 3-CHOME, CHIYODA-KU. TOKYO ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: HIROSE, HIDEO
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Assigned to NIKON CORPORATION, 2-3, MARUNOUCHI 3-CHOME, CHIYODA-KU, TOKYO, JAPAN reassignment NIKON CORPORATION, 2-3, MARUNOUCHI 3-CHOME, CHIYODA-KU, TOKYO, JAPAN CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). EFFECTIVE APR. 1, 1988 Assignors: NIPPON KOGAKU, K.K.
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B21/00—Microscopes
    • G02B21/06—Means for illuminating specimens
    • G02B21/08—Condensers

Definitions

  • the present invention relates to a telecentric illumination system. More particularly, the present invention is directed to improvements in such illumination system, and in which the illuminated area can be changed.
  • FIG. 1 illustrates an example of the simple illumination area changeover system according to the prior art.
  • FIG. 1A and 1B show two different states of illumination by use of an illumination system comprising a positive and a negative lens. The state of illumination shown in FIG. 1A is for a lower magnification and that shown in FIG. 1B is for a higher magnification.
  • the known illumination system has the drawback that when the magnification is changed from a lower magnification as shown in FIG. 1A to a higher magnification as shown in FIG. 1B, the marginal rays become unusable for illuminating the narrower area and therefore the efficiency of the illumination often drops down. This will be described in detail with reference to FIGS. 1A and 1B.
  • FIGS. 1A and 1B the sample surface to be illuminated is indicated by O. Dotted lines indicate oblique rays.
  • the composite focal length is relatively long, and therefore the beam diameter is relatively large.
  • the angle which the oblique rays form with the optical axis of the illumination system is small. Under this state of illumination, the quantity of marginal light incident on the sample surface (O) is sufficient.
  • condensing illumination has been employed in many apparatus, but only for want of a better technique.
  • the illumination system can no longer maintain the conditions for telecentric illumination.
  • Such illumination system can not be satisfactorily used as an illumination system for a measuring instrument or other similar apparatus for which extremely high accuracy is required.
  • the known illumination system also has a problem in measuring a cylindrical object.
  • a cylindrical object is illuminated by the above known illumination system, there is produced a partial shadow due to the effect of the illumination aperture.
  • the geometric boundary of the measured object and the optical boundary can not exactly coincide with each other, so that a measuring error is caused.
  • the illumination must be done through an aperture properly adjusted relative to the diameter of the measured object in accordance with the well-known Gunther's formula. "Die Microskopische Ab Struktur von Zylindern and Gewinden" appearing on pages 315-321 of Zeitschrift fur Instrumentekund, August 1939.
  • a telecentric stop aperture stop
  • variable power telecentric illumination system comprises a first converging lens group, a second converging lens group, a third diverging lens group and a fourth converging lens group arranged in this ordinal sequence as viewed in the direction toward the object side to be illuminated from the light source side.
  • the second and third groups are interchangeable in position.
  • An image of the light source by the composite system of the first and second groups is formed between the second and third groups.
  • the focal point on the light source side of the composite system of the third and fourth groups is coincident with the light source image.
  • the composite system of the first and third groups forms an image of the light source between the second and third groups.
  • the focal point on the light source side of the composite system of the second and fourth groups is coincident with the light source image.
  • the illuminated area on the object surface is changed by the interchange of positions between the second and third groups while maintaining the condition of telecentric illumination.
  • the four groups lens units are arranged in the following manner.
  • the first group forms an image of the light source at the middle point between the second and third groups.
  • the focal point on the light source side of the fourth group lies just at the middle point between the second and third groups.
  • the image point given by the second group regarding the middle point between the second and third groups as the object point of the second group becomes the object point of the third group.
  • the image point of the light source by the composite system of the first and second groups becomes the object point of the third group.
  • the image point of this object point by the third group is coincident with the above middle point.
  • the image point given by the third group whose object point is the middle point between the second and third groups becomes the object point of the second group.
  • the image point of the light source by the composite system of the first and third groups becomes the object point of the second group.
  • the image point of this object point by the second group is coincident with the above middle point.
  • the composite focal length of the lens groups between the light source image and the illuminated object can be made longer by locating the converging second group on the side of the first group and the diverging third group on the side of the fourth group.
  • the composite focal length of the lens groups between the light source image and the illuminated object can be made shorter by locating the diverging third group on the side of the first group and the converging second group on the side of the fourth group while increasing the magnification of the light source image and narrowing the illuminated area as compared with the state of illumination at the above lower magnification.
  • the change of the illuminated area can be attained by the interchange of positions between the second and third groups while maintaining the conjugated relation to the light source.
  • FIGS. 1A and 1B illustrate an illumination system according to the prior art showing the state of illumination at a lower magnification and at a higher magnification, respectively;
  • FIGS. 2A, 2B, 3A, 3B, 4A and 4B show various basic arrangements of the illumination system according to the invention in which A is for low magnification and B is for high magnification throughout all of the figures; and
  • FIGS. 5A and 5B show the optical path of an embodiment of the invention in which again A is for low magnification and B is for high magnification.
  • FIGS. 2A and 2B A basic arrangement of the illumination system according to the invention is shown in FIGS. 2A and 2B in two different positions, namely the position for low magnification 2A and the position for high magnification 2B.
  • the illumination system is composed of a converging first group L 1 , a converging second group L 2 , a diverging third group L 3 and a converging fourth group L 4 arranged in sequence as viewed from the side of a light source S.
  • the second and third groups L 2 and L 3 are interchangeable in position.
  • the image of the light source S by the first group L 1 and the focal point on the light source side of the fourth group L 4 are always coincident with each other at the middle point M between the second and third groups L 2 and L 3 .
  • the powers of the second and third groups L 2 and L 3 are predetermined in the following manner:
  • the image point I given by the second group regarding the middle point M as the object point of the second group L 2 corresponds to the object point of the third group L 3 , the image point of which is coincident with the middle point M.
  • the image point I given by the third group regarding the middle point M as the object point of the third group corresponds to the object point of the second group L 2 , whose image point is coincident with the middle point M.
  • the second and third groups L 2 and L 3 hold the following relations therebetween: ##EQU1## wherein, f 2 is the focal length of the second group L 2 ;
  • f 3 is the focal length of the third group L 3 ;
  • D is the distance between the groups L 2 and L 3 ;
  • b is the distance between the second group L 2 and the light source image I.
  • f 4 is the focal length of the fourth group L 4 .
  • Equation (9) has real solutions, which proves that there really exist two pairs of conjugate points which remain unchanged even by the interchange of position between the second and third groups L 2 and L 3 .
  • the solutions obtained from the equation (9) have different signs, (+) and (-).
  • the solution with (+) corresponds to the middle reference point M between the second and third groups.
  • the solution with (-) corresponds to another pair of conjugate points (C, C') existing outside of the second and third groups.
  • the first group L 1 is positioned at the conjugate point (C) on the side of the light source and the illuminated object surface is at the image point of the conjugate point on the object surface side by the fourth group L 4 .
  • the first group L 1 is positioned at the conjugate point (C) on the side of the light source and the illuminated object surface is at the image point of the conjugate point on the object surface side by the fourth group L 4 .
  • FIGS. 3A and 3B show another arrangement of the illumination system according to the invention.
  • a field stop FS is provided at the conjugate point (C) on the illumination source side and a telecentric stop TS, that is, an aperture stop is provided at the image point I of the light source S.
  • Other parts of the arrangement shown in FIGS. 3A and 3B correspond to those of the arrangement shown in FIGS. 2A and 2B.
  • the illumination aperture is reverse-proportional to the size of the illuminated field.
  • the illumination aperture becomes small
  • the illumination aperture becomes large
  • the aperture of an objective lens becomes smaller toward lower magnification and becomes larger toward higher magnification. Therefore, the use of the arrangement according to the invention has the advantage that the amount of aperture control necessary for an objective lens with high magnification as well as the amount of field control necessary for a high magnifying power objective lens can be substantially reduced as compared to the conventional arrangements thereby, attaining the more effective use of the beam of light for both of low magnification and high magnification. It is obvious that the stops may be omitted from the above shown arrangement in view of cost without losing the effect of the invention.
  • FIGS. 4A and 4B show a further arrangement of the telecentric illumination system according to the invention.
  • an additional converging lens L 1 ' is provided between the conjugate point (C) and the second group L 2 or the third group L 3 (as described above and shown in A and B, the second and third groups L 2 and L 3 are interchangeable in position).
  • the additional converging lens L 1 ' is so disposed that an image of the light source is formed at the middle point M by the first group L 1 and the converging lens L 1 ' and the conjugate point (C) lies at the inside of the focal point on the light source side of the converging lens L 1 '.
  • the following table shows a concrete embodiment of the basic arrangement shown in FIGS. 2A, 2B and 3A, 3B as numerical data of power shares of the groups L 1 , L 2 , L 3 and L 4 .
  • f 1 , f 2 , f 3 and f 4 are focal length of the groups respectively.
  • FIGS. 5A and 5B illustrate the optical path of the above embodiment and showing the the lenses in more detail.
  • FIG. 5A shows the position for illumination at a lower magnification in which a broader area is illuminated.
  • FIG. 5B shows the position for illumination at a higher magnification in which a narrower area is illuminated.
  • a telecentric stop TS is disposed at the position of the light source image between the converging second group L 2 consisting of a positive lens and the diverging third group L 3 consisting of a negative lens.
  • the second and third groups L 2 and L 3 and the telecentric stop TS are received in a lens tube 10 so as to form a unit.
  • the lens tube 10 is rotatable about an axis A containing the middle point between the second and third groups L 2 and L 3 . Therefore, the positions of the second and third groups L 2 and L 3 in the optical path can be interchanged by rotating the lens tube 10 about the axis A.
  • the relative position of the telecentric stop TS to the second and third groups remains unchanged. In this manner, the illumination system can be changed from illumination with low magnification to illumination with high magnification and vice versa in a very simple manner while maintaining the condition of telecentric illumination and without any problem of excess or shortage of effective light for illumination.
  • the illumination system of the invention has many advantages over the prior art.
  • the beam of light from a light source can be used more effectively for illumination in both of the position for illumination with low magnification and the position for illumination with high magnification. Therefore, good performance of telecentric illumination is always obtained.
  • the illumination system of the invention is applied to a measuring projection, which is usually used in a relatively bright room, the examiner can obtain a bright view field for observation even with a high magnifying power lens. Thereby the operability of the examining apparatus can be improved to a great extent.
  • a telecentric stop can be incorporated into a telecentric illumination system.
  • a field stop at the conjugate point on the light source side in addition to the above telecentric stop, it is possible to control both of the view field and the aperture.
  • the illumination system according to the invention may be used also as a magnification variable Kohler illumination system for common microscopes.

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  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Lenses (AREA)
  • Microscoopes, Condenser (AREA)
US06/388,200 1981-06-19 1982-06-14 Telecentric variable power illumination system Expired - Lifetime US4511223A (en)

Applications Claiming Priority (2)

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JP56093729A JPS57208523A (en) 1981-06-19 1981-06-19 Telecentric variable magnification lighting system
JP56-93729 1981-06-19

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0364794A3 (de) * 1988-10-05 1991-07-24 Firma Carl Zeiss Beleuchtungseinrichtung für Operationsmikroskope
US5200861A (en) * 1991-09-27 1993-04-06 U.S. Precision Lens Incorporated Lens systems
US5625495A (en) * 1994-12-07 1997-04-29 U.S. Precision Lens Inc. Telecentric lens systems for forming an image of an object composed of pixels
US5841587A (en) * 1996-04-29 1998-11-24 U.S. Precision Lens Inc. LCD projection lens
US6384968B1 (en) * 1999-05-31 2002-05-07 Asahi Kogaku Kabushiki Kaisha Microscope with illuminating optical system
US20030021035A1 (en) * 2001-06-06 2003-01-30 Kenichi Kusaka Microscope illumination optical system
US6578987B1 (en) * 2000-05-03 2003-06-17 Vari-Lite, Inc. Intra-lens color and dimming apparatus
US20030210856A1 (en) * 2002-05-10 2003-11-13 Cormack Robert H. Telecentric 1xN optical fiber switches
US20060007686A1 (en) * 2004-11-19 2006-01-12 Whiterock Design, Llc Stage lighting methods and apparatus
US20070268700A1 (en) * 2004-11-19 2007-11-22 Whiterock Design, Llc Optical system with array light source

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4043619B2 (ja) * 1998-10-26 2008-02-06 オリンパス株式会社 照明装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1236722A (en) * 1914-11-14 1917-08-14 Optische Anstalt Goerz Ag Optical system of variable magnification.
US3549230A (en) * 1967-03-15 1970-12-22 Nippon Kogaku Kk Zooming device for adjusting the light amount of a formed image
US3637282A (en) * 1970-02-21 1972-01-25 Olympus Optical Co Elongated variable magnification optical system having selectively interchangeable lenses
US4386828A (en) * 1980-05-26 1983-06-07 Nippon Kogaku K. K. Telecentric illumination system

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS509456Y2 (enrdf_load_html_response) * 1971-03-31 1975-03-24

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1236722A (en) * 1914-11-14 1917-08-14 Optische Anstalt Goerz Ag Optical system of variable magnification.
US3549230A (en) * 1967-03-15 1970-12-22 Nippon Kogaku Kk Zooming device for adjusting the light amount of a formed image
US3637282A (en) * 1970-02-21 1972-01-25 Olympus Optical Co Elongated variable magnification optical system having selectively interchangeable lenses
US4386828A (en) * 1980-05-26 1983-06-07 Nippon Kogaku K. K. Telecentric illumination system

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0364794A3 (de) * 1988-10-05 1991-07-24 Firma Carl Zeiss Beleuchtungseinrichtung für Operationsmikroskope
US5200861A (en) * 1991-09-27 1993-04-06 U.S. Precision Lens Incorporated Lens systems
USRE39424E1 (en) * 1994-12-07 2006-12-12 3M Innovative Properties Company Telecentric lens systems for forming an image of an object composed of pixels
US5625495A (en) * 1994-12-07 1997-04-29 U.S. Precision Lens Inc. Telecentric lens systems for forming an image of an object composed of pixels
US5841587A (en) * 1996-04-29 1998-11-24 U.S. Precision Lens Inc. LCD projection lens
US6384968B1 (en) * 1999-05-31 2002-05-07 Asahi Kogaku Kabushiki Kaisha Microscope with illuminating optical system
US6578987B1 (en) * 2000-05-03 2003-06-17 Vari-Lite, Inc. Intra-lens color and dimming apparatus
US6836358B2 (en) * 2001-06-06 2004-12-28 Olympus Corporation Microscope illumination optical system
US20050088733A1 (en) * 2001-06-06 2005-04-28 Kenichi Kusaka Microscope illumination optical system
US6898005B2 (en) * 2001-06-06 2005-05-24 Olympus Corporation Microscope illumination optical system
US20030021035A1 (en) * 2001-06-06 2003-01-30 Kenichi Kusaka Microscope illumination optical system
US20030210856A1 (en) * 2002-05-10 2003-11-13 Cormack Robert H. Telecentric 1xN optical fiber switches
US20060007686A1 (en) * 2004-11-19 2006-01-12 Whiterock Design, Llc Stage lighting methods and apparatus
US7226188B2 (en) 2004-11-19 2007-06-05 Whiterock Design, Llc Stage lighting methods and apparatus
US20070268700A1 (en) * 2004-11-19 2007-11-22 Whiterock Design, Llc Optical system with array light source
US20070285925A1 (en) * 2004-11-19 2007-12-13 Hough Thomas A Stage lighting methods and apparatus
US7901089B2 (en) 2004-11-19 2011-03-08 Whiterock Design, Llc Optical system with array light source
US8282245B2 (en) 2004-11-19 2012-10-09 Whiterock Design, Llc Stage lighting methods and apparatus

Also Published As

Publication number Publication date
JPS57208523A (en) 1982-12-21
JPS6319844B2 (enrdf_load_html_response) 1988-04-25

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